Electric field effects in nematic liquid crystals doped with carbon nanotubes

• We represented the current–electric field plots for pure nematic liquid crystal.
• We plotted the current–electric field for planar mixture of NLC and CNTs.
• We plotted the current–electric field for homeotropic mixture of NLC and CNTs.
• We made theoretical consideration to explain the currents in both cases.
• We studied the temperature change in electric current for mixture (NLC–CNTs).

The aim of this paper was to investigate electric field induced effects in mixtures of nematic liquid crystals (NLCs) with positive electric anisotropies (MCL 6601 Merck) with carbon nanotubes (MWCNT from Aldrich). In planar alignment, the current–electric field dependence and the current–temperature dependence were explained by assuming a Poole–Frenkel effect (i.e. a tunnelling mechanism) and good agreement with the experimental data was obtained. Within this high field range it resulted that in planar aligned NLC–CNTs mixture the conductivity decreases when the temperature was increased. In homeotropic aligned mixture, the conduction mechanism is similar to the one occurring in a semiconductor: the conductivity increases when increasing temperature. This happens because in thin liquid crystal cells there is a possibility to realize an inner contact between nanotubes and electrodes so the mixture behaves like a semiconductor.